| With the construction of water conservancy projects,highway projects and mining projects in different countries,a large number of flexural toppling failures have been discovered.Many scholars have proposed corresponding stability evaluation methods based on the mechanism of flexural toppling failure,and discussed the influence of various factors on slope stability.However,the proposed models are relatively simple.They all simplify natural anti-dip slopes into uniform-thickness homogeneous slopes,and there are few studies on more complicated non-equal-thick anti-dip rock slopes.Therefore,main researches of this Master's thesis are as follows:(1)The limit equilibrium method based on cantilever beam theory is a feasible method for analyzing flexural toppling in anti-dip layered rock slopes.However,most of the current calculation methods are iterated successively for all strata on the failure surface,which often requires a lot of mathematical calculation.It is difficult to evaluate the slope stability in the field quickly and preliminarily.Based on cantilever beam theory,the rock columns above the failure surface are divided into three sections: the stable section,the active toppling section and the passive toppling section by comparing the critical instability height with the present height of the block on the failure surface.Based on the limit equilibrium,the corresponding stability calculation method is proposed,and the risk of toppling failure can be preliminarily determined by using the geometric area.2 engineering examples and centrifuge experiments were illustrated for practical verification of the proposed approach.The research results of this paper have guiding significance and application value for the stability evaluation of flexural-toppling failure in rock slopes.(2)Flexural toppling often occurs in layered rock slopes,and rock columns behave like inclined superimposed cantilever beams that bend under their own weight.However,anti-dip rock slopes always have nonuniform joint spacing,and rock columns do not have the same ability of deformation due to different stiffness.To have the same deflection,based on the mechanics of materials,the moment and shear force at the failure surface should satisfy a certain proportional relationship.An analytical model based on deformation compatibility against the flexural toppling failure has been established.In the proposed model,the slope is divided into free deflection zones and compatible deflection zones by shear forces on the failure surface.The safety factor of each block can be calculated by the bending moment,andthe least factor is used to represent the safety of the slope.In addition,for an equal thickness model,the average stiffness method is suggested to determine the calculated thickness for foliated rock slopes with nonuniform joint spacing.Finally,a case study is used for practical verification of the proposed method.(3)Flexural toppling failure of anti-slopes with equal thickness layers has been studied by many researchers.However,in natural slopes,rock layers in anti-dip rock slopes always have unequal thickness.To analyze this condition,six slope models were manufactured by glass plates and conducted in geotechnical drum centrifuge.In these experiments,deformation and interlayer force characteristics obtained by cameras and film pressure sensors.Centrifugal test results show that the progress failure can be divided into three stages: failure of the slope toe,development of fractures and failure of slope.Initial toe failure has little effect on the stability of upper rock mass.Meanwhile g values of 4 models with unequal thickness layers are close to that of the model in test-2.Though centrifugal test and limit equilibrium method results,slopes with only the thick layer thickness can be used in the evaluation of stability of slopes with unequal thickness layers.This is because thicker strata have great bending stiffness and bending strength,which play an important role in slope deformation and stability. |
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